Russdl Posted October 16, 2016 Share Posted October 16, 2016 There doesn't seem to be a great deal of discussion about PHPP on these pages. I'm planning a passive house (not necessarily certified) new build and have convinced myself that it really should be done. I've read on these pages about problems with overheating but there is generally no information on whether the property in question had a PHPP and the overheating was predicted. I know of one property where there was no PHPP (it had been modelled, but not with PHPP) and, on first sight, I thought it looked like a building that would probably overheat. Sure enough, it has, and now requires remedial work to try and reduce the problem. I guess the question is 'does PHPP work?' Followed by 'how do you find a PHPP expert?' because some of the discussion indicates that there are some PHPP practitioners out there who perhaps are inept. 1 Link to comment Share on other sites More sharing options...
IanR Posted October 16, 2016 Share Posted October 16, 2016 If you "hung out" on the AECB Forum and posted a few questions then in the passed you may have got a few contacts, but I'm not sure how busy that Forum is these days. Other than that, you've probably asked in the right place and some recommendations will likely come along. I used Dr. Roderick Williams of Williams Energy and thought he was very good. I used him due to his association with Touchwood Homes, who supplied my frame. I'm pretty sure he takes on non-Touchwood work. Link to comment Share on other sites More sharing options...
Russdl Posted October 16, 2016 Author Share Posted October 16, 2016 Much appreciated Ian. Link to comment Share on other sites More sharing options...
Gone West Posted October 17, 2016 Share Posted October 17, 2016 I bought a copy of PHPP seven years ago and used it to help design my house which is being built to PH criteria. I did design in a large glazed area facing WNW which did cause some overheating in mid summer which was predicted. I have mitigated the effect by using a solar film. I have visited several PH, two of which were designed by PHPP experts but I was not impressed. If you have a scientific background, or not maybe, and read the manual a couple of times before starting to use the spreadsheet I can't see why it can't be used by a non 'expert'. It would at least give you an idea of what you want and input data can be tweaked easily to change results. 1 Link to comment Share on other sites More sharing options...
le-cerveau Posted October 17, 2016 Share Posted October 17, 2016 @PeterStarck +1. I also bought PHPP, after much soul searching, it is not that expensive in the grand scheme of thighs and I just followed the instruction book. I am sure what I have is not perfect but close enough to give me an idea, play with wall/roof insulation options etc. I don't have an overheating problem, no large glazing elements (stand fast one NW long and wide stair window) and in Cumbria so not exactly hot! It does however allow me to look at what will happen, if I drop the overheat temp from 25oC to 23oC then there is some overheating, not much, so I have made provision for slab cooling (as in JSH design) and heat redistribution (but that is another topic). Link to comment Share on other sites More sharing options...
jack Posted October 17, 2016 Share Posted October 17, 2016 It's been ages since I looked at this, but from memory one of the sheets has an overheating factor, which is the amount of time (as a percentage of days? Not sure) the house will be above a target temp. You can set that temperature as well. From memory, the default setting aren't very conservative - something like 24 or 25 degrees for 5% of the days each year. That's actually quite hot in a Passivhaus, and quite a lot of days. I seem to recall reading that you should reduce the temp setting and do what you need to do to bring the 5% down to 1-2%. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted October 17, 2016 Share Posted October 17, 2016 Have been using PHPP myself to drive our architect along - acting as the consultant. Overheating was a massive problem with too much south facing glass but now we are in at 5% with the final glazing scheme. I have got it down to 1.9% overheating with my latest model of the summer ventilation scheme this is the best I can get it but will probably drop it back to 5% because 1.9% means leaving large windows fully open - shows you how much control you have. Its not hard to get a house up and running on PHPP and provided you answer the questions you don't need to be a building scientist to make it work. I did the 1 day intro course at BRE it comes with a free copy of the software and I thought is was good value for money. Link to comment Share on other sites More sharing options...
le-cerveau Posted October 17, 2016 Share Posted October 17, 2016 @jack just checked on PHPP it is 25oC and 10% of overall days, as you say quite hot in a Passive type house, you can adjust the temperature not the percentage. the 25/10 is for PHPP certification (I suspect), in reality I think 23oC is a more realistic target to aim for if you want a truly comfortable house and the PHPP software lets you play around. You can change MVHR unit which can have an effect (one thing I did), change the specifications of each individual window, all sorts or options. Link to comment Share on other sites More sharing options...
IanR Posted October 17, 2016 Share Posted October 17, 2016 Out of interest, those that have done the PHPP themselves, how many hours do you think you spent using the PHPP software to initially model and then iterate the design options? I liked the thought of doing it myself, but felt it would end up demanding more hours than I had available at the time. Link to comment Share on other sites More sharing options...
le-cerveau Posted October 17, 2016 Share Posted October 17, 2016 It is not quick, you need the full details for the house, dimensions, windows location type, the works, so there is a lot of information you need or have to assume. Even if you paid someone to do it you would have to provide them with the info so it would take probably just as much time! I spend an hour or two a night for a couple of weeks, working through the book and filling in the details into the system and I had a lot of info to start with. As I say you will need to do a lot of work either way! 1 Link to comment Share on other sites More sharing options...
Russdl Posted October 17, 2016 Author Share Posted October 17, 2016 Thanks for the answers so far. Much like Ian, I don't feel I have the available time, but I have an older, much wiser, semi-retired brother who does so I'm going to delegate to him. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted October 17, 2016 Share Posted October 17, 2016 (edited) Around 10 hours on top of the course to get V1 done. From then on every iteration to tackle issues you find demands adjustments until you get it all clear with the architect. Yesterday I spent about 3 hours going through changes caused by getting the windows all into BC spec (openable at the right height) and playing with the insulation as the cost of the type specified by the architect was too great so I found another one, higher U value and adjusted all the areas to see what happened and we are still in the envelope so will go back to Architect and get spec changed and so it goes on.... Edited October 17, 2016 by MikeSharp01 Link to comment Share on other sites More sharing options...
jack Posted October 17, 2016 Share Posted October 17, 2016 1 hour ago, le-cerveau said: @jack just checked on PHPP it is 25oC and 10% of overall days, as you say quite hot in a Passive type house, you can adjust the temperature not the percentage. the 25/10 is for PHPP certification (I suspect), in reality I think 23oC is a more realistic target to aim for if you want a truly comfortable house and the PHPP software lets you play around. You can change MVHR unit which can have an effect (one thing I did), change the specifications of each individual window, all sorts or options. 10%? It's worse than I remembered! Given that there's very little chance of overheating for most of the year, this suggests that maybe 20-50% of the days in the hottest part of summer will result in temps above 25 degrees. I don't think that's acceptable at all. One thing I do wish we'd factored in is insect screens, at least in bedroom windows. That way we could leave them open all night in summer to maximise purging of hot air without letting mosquitoes in. Link to comment Share on other sites More sharing options...
IanR Posted October 17, 2016 Share Posted October 17, 2016 49 minutes ago, jack said: Given that there's very little chance of overheating for most of the year, this suggests that maybe 20-50% of the days in the hottest part of summer will result in temps above 25 degrees. I don't think that's acceptable at all. +1 It was explained to me the % overheating is in respect to the number of hours per year that would be over 25 degrees. PH rate the scale as: 0-2 Excellent, 2-5 Good, 5-10 acceptable However, working through this with Rod Williams, we didn't feel 5-10% was at all acceptable, so we made changes to bring the initial risk of 15% down to 1.5%. However, the advice I got was to not rely on manual processes like having to physically open a vent. Ideally you'd get to the Excellent range by passive means, and if not possible* then by automated means. * = not willing to compromise on that large glazed facade Once you are in the Excellent range there should then be manual process (opening windows etc.) available to then resolve the "extreme" conditions. Link to comment Share on other sites More sharing options...
PeterW Posted October 17, 2016 Share Posted October 17, 2016 9 minutes ago, IanR said: However, the advice I got was to not rely on manual processes like having to physically open a vent. Ideally you'd get to the Excellent range by passive means, and if not possible* then by automated means. * = not willing to compromise on that large glazed facade Once you are in the Excellent range there should then be manual process (opening windows etc.) available to then resolve the "extreme" conditions. So for a PHPP thicko like me ... that means the house either has to have the overheat issue designed out, or have some automated means to control the solar gain and heating effect...?? It would be interesting to see if the model can cope with the steady and slow rise in U.K. Temperature - I know the Met Office 5/10/20 year average data is starting to become fairly pointless as it's not granular enough to cope with the extremes such as a drought/flood cycle. Link to comment Share on other sites More sharing options...
IanR Posted October 17, 2016 Share Posted October 17, 2016 2 hours ago, MikeSharp01 said: Around 10 hours on top of the course to get V1 done. That seems really efficient to me, and much quicker than I would have expected. How granular have you gone with your fabric model? Do you have approximate U Values for walls and roof or have you modelled all potential cold bridge areas ie. extra structure around windows, doors, eaves and true timber fraction etc. I'm sure it's a case of diminishing returns (to accuracy), and no idea at what point the critical mass of detail is achieved. 6 minutes ago, PeterW said: So for a PHPP thicko like me ... that means the house either has to have the overheat issue designed out, or have some automated means to control the solar gain and heating effect...?? In my case I wasn't willing to reduce glazing to a sufficient level so have used automated external blinds to bring the overheating risk into the excellent range. In PH Certification context, I don't believe that means it has been designed out, whereas if I had used fixed brise soleil it would have done. Link to comment Share on other sites More sharing options...
jack Posted October 17, 2016 Share Posted October 17, 2016 1 hour ago, IanR said: It was explained to me the % overheating is in respect to the number of hours per year that would be over 25 degrees. It keeps getting worse. A house that stays over 25 degrees for fully 10% of the entire year is crazy! Worse, it'll typically be the bedrooms that are warmest. To be fair, I don't think many PH consultants, or even the PH Institute themselves, would recommend designing to just the "acceptable" range if it's avoidable. 10% really is a minimum standard, and you'd hope that anyone with basic experience and training would encourage people to get as close to the excellent range as possible. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted October 17, 2016 Share Posted October 17, 2016 8 hours ago, IanR said: That seems really efficient to me, and much quicker than I would have expected. How granular have you gone with your fabric model? Do you have approximate U Values for walls and roof or have you modelled all potential cold bridge areas ie. extra structure around windows, doors, eaves and true timber fraction etc. I'm sure it's a case of diminishing returns (to accuracy), and no idea at what point the critical mass of detail is achieved. In my case I wasn't willing to reduce glazing to a sufficient level so have used automated external blinds to bring the overheating risk into the excellent range. In PH Certification context, I don't believe that means it has been designed out, whereas if I had used fixed brise soleil it would have done. I did go through the wall build ups I did not model the thermal bridges round the wondows as I am not sure it would help as we are trying not have any thermal bridges around them and in the PHPP I worked on the assumption that the wall U value moves from Wall to Window on the boundary which is somewhat why the windows have to set up carefully in terms of edges in contact with what in the windows sheet. There is always the what I think of as the zero sum rule to help decide if a bridge exists / needs detailed modelling or not! You are dead right you can work away squeezing 100ths here and there but get blown away by the wrong MVHR I was worried when ours was not a passive house and I modelled thicker walls, better insulation to get it back into spec only to find that I must have scrolled through the available MVHR and landed on one with 80% efficiency rather than the 91% I had intended, and still do, to use. Suddenly I could get away with thinner walls, cheaper insulation. I guess this means just keep doing your reality checks! I am happy with 5% overheadting - thats still 18 days. I can get it way down by opening the windows but then we have a security - rather bigger than mosquitos, problem. Link to comment Share on other sites More sharing options...
Stones Posted October 17, 2016 Share Posted October 17, 2016 Overheating is an interesting one. I too would find 25C unacceptable for anything other than a very short duration, but I want glazing to take in the views, which due to our orientation, does mean that there would be some overheating in summer. For me, it's a case of mitigating the impact, and I can do this using the summer bypass on the MVHR. I based all of my heating / cooling requirements on maintaining 21C. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted October 20, 2016 Share Posted October 20, 2016 Hi All - Just received notification of this document which is essentially the the course I spoke of above. Has everything you need to under stand and deliver a 'COOL' home. Mike 2 Link to comment Share on other sites More sharing options...
Russdl Posted October 20, 2016 Author Share Posted October 20, 2016 Thanks very much Mike, that should make for very interesting reading - I appreciate your post. Russ. Link to comment Share on other sites More sharing options...
Russdl Posted June 26, 2017 Author Share Posted June 26, 2017 Well, I've been on the back burner for a while (again), but slowly making progress-ish. I chickened out and went for a PHPP consultant who has sent me a copy of his first iteration of my plan, having looked through it I'm concerned about several things, the main one being the 'DEVIATION FROM NORTH' on the 'SHADING' tab. Without leading anyone with his or my view, I would be very grateful for anyones input on what they consider the 'DEVIATION FROM NORTH' of the wall highlighted in red on the image below - ball park is fine, the consultant and I differ by 60 degrees. Thanks in advance. Link to comment Share on other sites More sharing options...
jack Posted June 27, 2017 Share Posted June 27, 2017 Eyeballing it, 120 degrees (or 60 degrees west). Edited to add: I have no idea what convention is used in this context. Link to comment Share on other sites More sharing options...
PeterW Posted June 27, 2017 Share Posted June 27, 2017 Looks like he is saying that the rearward wall will be shaded (from morning sun) however I can't work out where the 120 degrees comes in unless he is saying that the right corner is pointing 120 degrees from north ..?? Link to comment Share on other sites More sharing options...
IanR Posted June 27, 2017 Share Posted June 27, 2017 (edited) My guess would be roughly 220 degrees or -140 degrees Edited June 27, 2017 by IanR adjusted the guess... Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now